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The old method of tire setting, as our readers are well aware, consists in first expanding the tires by heat and then allowing them to contract upon the wheels. In this way a powerful—sometimes too powerful—pressure is brought to bear upon the wheel, consolidating its parts and increasing what is known as the dish of the wheel. A patent has been recently taken out in England for an entirely new method of setting tires without heat, which, while we are not prepared to admit the value claimed tor it, is sufficiently ingenious to warrant some notice ; and if on trial it should be found to answer the purpose, it will really be an important improvement. The invention is based on the general principle that action and reaction are equal. In a wagon wheel the tire cannot exert any greater pressure upon the woodwork than the woodwork exerts upon the tire. If then, the woodwork can be contracted and permitted to expand against the interior of the tire, the same efl'ect would be produced as is now obtained by the contraction of the tire. If a wheel be laid fiat, and supported only by a circular bearing on which the side of the rim rests, no other part being supported, and downward pressure be applied to the hub, a contraction of the rim will take place relatively to the dish given to the wheel by the pressure on the hub, provided the rim were so firmly attached to the spokes, and the spokes to the hub, that no withdrawal could take place. As, however, the parts of a wheel are not so strongly attached to each other as to overcome the resistance of the rim to pressure, the method we are describing employs also external pressure upon the rim of the wheel, an hydraulic pump being employed to generate the required pressure. As the pressure is applied and the wheel contracts, it is made to descend into a funnel-shaped support, so that ?vhen the external pressure is taken off of the rim, the pressure upon the_hub,givingdishto the wheel,being still maintained, the contraction of the rim is kept up till the tire is placed around it. The hub being next released from pressure, the elasticity of the woodwork carries the hub back to its normal position with reference to the other parts of the wheel, a general expansion takes place, and the tire becomes permanently set. It is said that the method can be applied with great rapidity and that the results seem satisfactory. It can, within certain limits, be applied to wheels of different diameters, and with greater economy than the old method of heating, a saving in time and labor, as well as a total saving of fuel being secured. Our readers will concede the ingenuity of the system, but will probably share our doubts in regard to its excellence ; nevertheless, it may prove upon extended trial to be just the thing required. If so, it will be another demonstration, that even in those things long generally regarded a having reached the limit of impuovement, there is still scope for inventive genius.
